Experimental study on loss and flow mechanism of variable stator vanes in high-pressure compressor with bleed

In modern compressors, variable stator vanes are increasingly utilized. These vanes require a specific gap between their leading and trailing edges and the casing/hub to prevent contact during rotation. For multi-stage axial compressors employing variable stator vanes, understanding the impact of clearance variations on compressor performance is crucial during design. This study focuses on experimental research conducted on a high-pressure compressor equipped with variable stator vanes and bleed, using a real engine structure. The investigation delves into the loss characteristics and flow mechanisms within the variable mechanism's flow field. Results show that, with the identical penny diameter, increasing radial clearance initially decreases flow field loss, but then loss rises, reaching a minimum with a 2 mm (1.25% blade height) clearance. Conversely, with the same radial clearance, increasing penny diameter initially increases loss, which then decreases, with larger penny diameters resulting in smaller losses. Based on these findings, it can be inferred that a clearance of around 2 mm substantially reduces losses within the vane. Losses within 0–10% of the blade height from the endwall mainly stem from penny leakage vortex and their interaction with passage vortex, while losses within 10–20% of the blade height primarily arise from passage vortex, thus mitigating overall losses. The study demonstrates that, compared to zero-clearance vanes, variable stator vanes with a partial gap resulted in lower total pressure losses and better flow field control.